1. The Field of the Invention
This invention relates generally to data communication systems employing a wireless communication channel. More particularly, the invention relates to minimizing data transfer rate renegotiations for transfer of data between modems.
2. Present State of the Art
Telecommunication systems traditionally facilitate the exchange of data between a data generator and a data recipient over a fixed or hard-wired communication channel. Such communication channels have taken forms such as local or wide area networks having hard-wired or coaxially-coupled links between data generators and data recipients such as computers. Even more popular than the aforementioned networks, the standard telephone network provides yet another hard-wired communication channel through which data may propagate. Such hard-wired communications channels typically exhibit very high and stable signal-to-noise ratios due to limited and stable interference parameters.
In a hard-wired or land line communication channel, a data generator and a data recipient negotiate, as a result of the ambient signal-to-noise ratio present at the commencement of a communication session, a data transfer rate for use over the existing wired communication channel. Upon the completion of a successful data transfer rate negotiation, the data generator transmits data at the negotiated data transfer rate to the data recipient via the wired communication channel. Due to the stable nature of wired communication channels, the data generator and data recipient continue to exchange data at the negotiated date transfer rate while the signal-to-noise ratio remains hospitable. When transient noise or degeneration of the wired communication channel occurs, the data generator and data recipient may renegotiate a more conducive data transfer rate. Such data transfer renegotiation processes such as those defined by popular standards, V32, V32bis, and X2, facilitate the renegotiation of a data transfer rate during an on-going communication session. However, renegotiation processes at the physical connection layer of the communication channel may require a retraining duration in excess of 30 seconds including the reestablishment of error correction and data compression protocols. In a highly stable wired communication channel where renegotiation processes are rare, the renegotiation time may easily be compensated for by the enhanced bandwidth or reliable channel resulting from the renegotiation process.
Conversely, wireless communication channels, such as those employed by cellular and other mobile communication technologies, exhibit a more divergent signal-to-noise ratio profile. As wireless communication channels freely propagate with other wireless communication channels through a shared propagation medium, such communication channels become susceptible to interfering signals and propagation conditions. While signal-to-noise ratios between a stationary wireless transmitter and a stationary wireless receiver may exhibit reasonably consistent signal-to-noise ratios, any mobility of either a wireless transmitter or receiver alters the propagation path through which data information must pass. Such perturbances to a communication channel affects the signal-to-noise ratio as perceived between the wireless transmitter and wireless receiver.
A data generator and recipient, such as personal computers, may employ a modem for modulation or demodulation of data prior to transmission or following reception of transmitted data. In an architecture where a modem selects a wireless communication channel through which to transmit and receive data, the modem performs a data transfer rate negotiation similar to that performed in a land or wired communication channel topology. The data transmitter and receiver engage in a data transfer rate negotiation process to determine a conducive data transfer rate for the then-present signal-to-noise ratio. For stationary modems and wireless transceivers, a reasonably stable signal-to-noise ratio may be perceived. In such an environment, a modem connected with a wireless transmitter may dispatch data to a wireless receiver, also connected to a demodulating modem, with infrequent renegotiation of the data transfer rate. However, when either a wireless transmitter or wireless receiver become mobile, the signal-to-noise ratio exhibited across the wireless communication channel varies greatly depending upon, among other things, the proximity of the wireless transceiver to the corresponding base station and the presence of interfering structures. In a cellular wireless communication environment, a mobile wireless transceiver traversing a minimal geographical area may approach and recede from numerous base stations. Such a change in the physical proximity of the wireless transceiver to the base station manifests a signal-to-noise ratio profile having a frequency of change dependent upon the relative mobility of the wireless transceiver.
Such a fluctuating signal-to-noise ratio requires that the transmitting modem and the receiving modem renegotiation a data transfer rate conducive to the then-present signal-to-noise ratio. In such a dynamic mobile environment, frequent data transfer rate renegotiations have been noted to occupy a substantial amount of time and bandwidth of the wireless communication channel between the data transmitter and receiver. While some prior art solutions have allowed a user to request the modem invoke a conservative data transfer rate for such dynamic communication channels, the solutions have required user intervention to configure the modem to conform with such a conservative or default data transfer rate. Such prior art solutions burden the user to notify the modem of the request for a conservative data transfer rate and furthermore locks the data transfer rate into a conservative value even when the wireless transmitter and receivers revert to a stationary, and hence a continuous signal-to-noise ratio, configuration.
Thus, what is needed is a method and system for revising an minimizing renegotiations of a data transfer rate when variations to the mobility of the modem, and hence wireless transceiver, is detected. Furthermore, what is desired is a method and system for providing automatic and continuous detection of the mobility of the modem thereby precluding intermittent renegotiation resulting from interim changes in signal-to-noise ratios.